Re: [PATCH] fix NFSv4 acl detection on F39

[Jeff Layton]

On Mon, 2023-05-15 at 17:28 +0000, Trond Myklebust wrote:
> On Mon, 2023-05-15 at 13:11 -0400, Jeff Layton wrote:
> > On Mon, 2023-05-15 at 11:50 +0000, Ondrej Valousek wrote:
> > > Hi Paul,
> > > 
> > > Ok first of all, thanks for taking initiative on this, I am unable
> > > to proceed on this on my own at the moment.
> > > I see few problems with this:
> > > 
> > > 1. The calculation of the 'listbufsize' is incorrect in your patch.
> > > It will _not_work as you expected and won't limit the number of
> > > syscalls (which is why we came up with this patch, right?). Check
> > > with my original proposal, we really need to check for
> > > 'system.nfs4' xattr name presence here
> > > 2. It mistakenly detects an ACL presence on files which do not have
> > > any ACL on NFSv4 filesystem. Digging further it seems that kernel
> > > in F39 behaves differently to the previous kernels:
> > > 
> > > F38: 
> > > # getfattr -m . /path_to_nfs4_file
> > > # file: path_to_nfs4_file
> > > system.nfs4_acl                                    <---- only
> > > single xattr detected
> > > 
> > > F39:
> > > # getfattr -m . /path_to_nfs4_file
> > > # file: path_to_nfs4_file
> > > system.nfs4_acl
> > > system.posix_acl_default
> > > /* SOMETIMES even shows this */
> > > system.posix_acl_default
> > 
> > (cc'ing Christian and relevant kernel lists)
> > 
> > I assume the F39 kernel is v6.4-rc based? If so, then I think that's
> > a
> > regression. NFSv4 client inodes should _not_ report a POSIX ACL
> > attribute since the protocol doesn't support them.
> > 
> > In fact, I think the rationale in the kernel commit below is wrong.
> > NFSv4 has a listxattr operation, but doesn't support POSIX ACLs.
> > 
> > Christian, do we need to revert this?
> > 
> > commit e499214ce3ef50c50522719e753a1ffc928c2ec1
> > Author: Christian Brauner <brauner@kernel.org>
> > Date:   Wed Feb 1 14:15:01 2023 +0100
> > 
> >     acl: don't depend on IOP_XATTR
> >     
> > 
> 
> 
> No. The problem is commit f2620f166e2a ("xattr: simplify listxattr
> helpers") which helpfully inserts posix acl handlers into
> generic_listxattr(), and makes it impossible to call from
> nfs4_listxattr().
> 


Ahh ok. Looking at that function though, it seems like it'd only report
these for mounts that set SB_POSIXACL. Any reason that we have that
turned on with v4 mounts?

This patch fixes the bug for me, but I haven't done any testing with it:

---------------8<-----------------

[RFC PATCH] nfs: don't set SB_POSIXACL on NFSv4 mounts

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfs/super.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 30e53e93049e..cbb8de6e25dc 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1057,7 +1057,6 @@ static void nfs_fill_super(struct super_block *sb, struct 
nfs_fs_context *ctx)
                sb->s_export_op = &nfs_export_ops;
                break;
        case 4:
-               sb->s_flags |= SB_POSIXACL;
                sb->s_time_gran = 1;
                sb->s_time_min = S64_MIN;
                sb->s_time_max = S64_MAX;
-- 
2.40.1